The principal objective of this study is to elucidate the hormonal feedback mechanisms involved in the control of glucagon, insulin, and somatostatin synthesis and release by the use of homogenous populations of pancreatic islet alpha (A) cells, beta (B) cells, and D-cells. The innovative cell separation technique, magnetophoresis, is being used to separate the pancreatic islet cells into homogenous subpopulations of the A-, B-, or D-cells. During the first year of this study we have developed a technique to produce monodisperse populations of rat islet cells which retain high viability and responsiveness. We have examined the uptake and metabolism of glutamate, GABA, and related amino acid analogs in these cells. The primary focus for the second year of these studies will be the production of monoclonal antibodies (via hybridomas) with islet cell type specificity. These antibodies will then be utilized to effect the separation of the monodisperse cell population now available. We also plan to continue the examination of the metabolism of GABA to elucidate its role in pancreatic islet cells.